1. Field of the Invention
The present invention is generally related to a multiple display system utilizing common display control hardware and, in particular, to an optimized system for enabling the display of independent video information simultaneously on multiple displays by a single display controller.
2. Description of the Related Art
Current developments in computer system architectures, particularly typified by those used in the personal computing environment, reflect a growing emphasis on the visual display of data. The diversity of types of data displayed and the amount of data desirably displayed concurrently is increasing. Conventional personal computer systems have met this demand by providing multiple independent display adapters, each supporting the separate display of image data, to be attached to a single computer system. While this approach does permit each adapter to optimally provide for the separate generation of the image data, there is no mutual optimization within the display sub-system as a whole.
The personal computing environment is highly competitive, both in terms of cost and performance. The utilization of multiple display adapters in a single personal computer system is disadvantageous based on the substantial cost of separate display adapters that each must meet the highest possible requirements of the video display sub-system. If dissimilar display adapters are utilized, in an effort to thereby reduce cost, a significant constraint is imposed on the computer system as a whole to correctly direct display images of appropriate complexity to display adapters of corresponding capability. This selection of target display adapter may not readily be managed by the personal computer system without intervention by the computer system user. Furthermore, use of display adapters of dissimilar display capabilities imposes a physical limitation on the images that can be displayed on any particular display device.
Other related factors that are involved in the selection of a display sub-system include chip count on the display adapters, the reliability of multiple adapters, power consumption requirements, system resource consumption, and physical size requirements to support the video display sub-system. For reducing chip count and increasing reliability, as well as reducing power consumption, the number of integrated circuit chips required to support multiple independent displays should be minimized. The manufacturing cost associated with reduced chip count should also result in a cost savings in addition to a reduction in the physical space, specifically the printed circuit board space, required to implement the video display sub-system.
The necessarily competing requirement, however, is the necessity for maintaining compatibility with existing defacto standard display adapter specifications. Display adapter designs are, to maintain competitive, at least compatible with an existing display adapter standard such as the standard know as "VGA". Conventional display adapters utilize integrated circuit chip sets to implement this standard and provide for the display of a single image on a video display console. Conventional chip sets may also provide for the concurrent display of a single image on multiple video devices. This is generally performed by duplicating the output video data and control signals to provide for the simultaneous drive of separate display devices. Conventionally, however, no provision is made for the ability to support separate displayed images from a single chip set display adapter. Where multiple independent displayable images are required, the conventional design approach is to provide multiple video controller chip set for the generation of respective images on multiple display adapter boards. Even if the multiple chip sets are implemented on a common single printed circuit board, such conventional implementations fail to significantly reduce the required chip count and, thereby inherently are of lesser reliability, higher cost and consume a greater amount of power.